opening up and extra hole on the cowling what is the negative of doing that?

I hear some people saying they opened up the holes on the cowling all four or two i have the factory hole open and i was wondering what is the negative of having two open or more? does water get in much easier? not all the holes have the tubing behind them i cant tell which one does but i think its only one or two?

The one on the right is blocked off to keep water from going into the dryer vent tube on the right. That dryer vent tube points right at your carbs. If you cut the one on the right open, I would either remove the dryer hoses or atleast re-route the one on the right so that it's not pointing at the carbs.

i found when i cut the hole for my humminbird 210 depth finder where the on-off-reserve valve was for the carbed models that i definately was starving for air as their was a marked improvement in performance. this is directly above my K&N filter, as i was filling that hole with the humminbird i drilled another hole down farther behind the right side panel centered above the two ellen screws that secure the bottom of the panel ( about five inches up) I cut it with a 2 1/4 hole saw and put a bead of marine silicone around the rim of the hole to reduce splash into the hull. worked great. also opened up the tops of the inner panel supports where the plastic tubes meet the hull. about double of the factory openings.

I have two visors. One I completely cut out the entire visor and the second I drilled holes. I drilled holes in the front bucket. I removed all the air duct hoses and containers that go to the air box. Basically left the opening of the air box open. Pulled the screens out of the air box. Drilled a hole on each side of my seat and on my other ski, drilled two holes out the back and put those black screen things that Jerry sells in his stores. I also drilled holes in my battery box. My ski gets plenty of air, cause with the bucket/visor open and the seat off, I gain no rpms. Hope this helps out.
I've also tried running the efi without the air box. Just left the booties on and rode it. Although it felt good I thought that with the air box for my ski that is, it hit harder with it on. So I put the airbox back on. Each ski is different, so try different things and record them to see what you like.
Some like running their skis without trim tabs, I prefer to have mine on. Things like that are your choices. Remember though, if you drill into the hull to keep the pieces for later in case you want to put it back in. Also wash the hull out really good afterwards so you don't get that stuff in your carbs.
Hope this helps
SHOOTER